Engine Fuel-Cut Airflow Control for Catalyst Thermal Shock
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Solution Overview
Problem
Existing catalyst devices in engines are prone to damage due to rapid cooling when exposed to high temperatures, which can occur during fuel cuts, leading to potential cracking and deterioration.
Innovation Solution
A control system that adjusts intake air amount using an intake air amount adjustment device, such as a throttle valve, to manage catalyst temperature by increasing air intake during fuel cuts when the catalyst temperature exceeds a predetermined threshold, and adjusting the rate of air intake based on the catalyst temperature to prevent excessive cooling or heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a large amount of air is introduced into the exhaust passage to cool the catalyst device, then the catalyst device temperature is reduced, but the catalyst device may suffer from thermal shock causing cracks or damage
Solution Approach 1:
The patent applies dynamics by making the intake air amount adjustable based on catalyst temperature conditions. The intake air amount adjustment device dynamically modifies the amount of air introduced into the exhaust passage according to real-time catalyst temperature, allowing the system to adapt between cooling needs and thermal shock prevention
Solution Approach 2:
The patent changes the parameter of intake air amount based on catalyst temperature. When catalyst temperature is high, a larger amount of air is introduced for cooling; when temperature is low, a smaller amount is introduced to avoid excessive cooling and thermal shock. This parameter adjustment resolves the contradiction between cooling effectiveness and device integrity
2Speed
If the intake air amount is increased rapidly to cool the catalyst device, then cooling efficiency is improved, but thermal shock may cause cracks in the catalyst device
Solution Approach 1:
The system dynamically adjusts the rate of air introduction based on catalyst temperature. The intake air amount adjustment device modifies the air flow rate in real-time, allowing rapid cooling when needed while preventing excessively fast cooling that would cause thermal shock and cracks
Solution Approach 2:
The patent changes the parameter of air introduction rate based on catalyst temperature conditions. By adjusting this parameter dynamically, the system achieves efficient cooling when catalyst temperature is high while avoiding rapid temperature drops that would cause thermal shock and structural damage
3Reliability
If fuel cut is implemented to reduce emissions, then exhaust gas purification is improved, but catalyst device temperature may become excessively high causing deterioration
Solution Approach 1:
The patent introduces air as an intermediary substance during fuel cut operation. By controlling the intake air amount adjustment device to introduce a large amount of air into the exhaust passage during fuel cut, the system uses this air as a cooling medium to prevent catalyst overheating while maintaining the emissions benefits of fuel cut
Solution Approach 2:
The system implements periodic or conditional air amount adjustment during fuel cut operations. The intake air amount is increased specifically during fuel cut periods when catalyst temperature tends to rise, creating a periodic cooling action that maintains purification performance while preventing excessive temperature accumulation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents catalyst device damage by controlling intake air amount to maintain optimal temperature, ensuring the catalyst device is neither excessively cooled nor heated, thereby preserving its performance and extending its lifespan.
Implementation Method 1
a catalyst device provided in the exhaust passage to purify exhaust gas
Implementation Method 2
a large amount of air is introduced into the exhaust passage and therefore into the catalyst device, and the catalyst device is cooled with the air
Data Source
AI summary
When an accelerator opening degree is equal to or less than a predetermined accelerator determination opening degree, a control device implements a fuel cut that stops fuel injection by an injector; and when the fuel cut is implemented while a catalyst temperature is equal to or higher than a predetermined determination temperature, the control device implements an intake air amount increase control that controls an intake air amount adjustment device so that an intake air amount is larger than while the catalyst temperature is lower than the determination temperature, and the control device controls the intake air amount adjustment device so that an increase rate of the intake air amount is decreased as the catalyst temperature increases.